The invention is related to the field of radio direction finding and in particular to direction finding by means of circular or cylindrical arrays of antenna elements and associated radio receiving apparatus. Numerous direction finding systems of the prior art employ a circular or cylindrical array of element antennas. Some of the prior systems are suitable for radio direction finding in a range of source directions that is generally broadside to the antenna array, i.e. in the general direction of an axis which is perpendicular to a plane of the circular array of element antennas. Other circularly arrayed direction finding systems of the prior art are suitable for direction finding in and near the plane of the circle of the array. For convenience, directions measured in the plane of the array will be referred to hereinafter as azimuth directions, although no limitation is intended thereby with regard to the orientation of the antenna systems relative to other objects such as a supporting vehicle or the earth. Most azimuth direction finding systems of the prior art have azimuthally directional antenna radiation patterns. For example, a single steerable beam of sensitivity, occupying generally a small sector of the complete azimuthal circle, is provided, which continually revolves through 360.degree. azimuth to locate the azimuth direction from which a target radio wave is coming. In such prior art systems every direction of azimuth is examined once during each revolution of the steerable beam, and each direction is examined for only a fraction of the period of revolution of the steerable beam.